implement candidate compromise proposal for websockets
1. Text and binary frames are accepted
2. Text frames are sent by default
3. Binary frames are sent to clients who negotiate `binary.ircv3.net`
4. Non-UTF8 data is not accepted (enabling websockets still enables UTFONLY)
mitigate a potential DoS against websocket listeners
Websocket listeners would process an arbitrary number of invalid
(non-text or blank) messages without throttling. This imposes fakelag
on such messages by treating them as blank lines.